Our laboratory is primarily concerned with the regulatory mechanisms which control the different functional levels of the microcirculation in skeletal muscle and skin. The investigative design is based on the general hypothesis that at least one functional level in the microcirculation is principally involved in the control of oxygen delivery to, and carbon dioxide removal from peripheral tissues, and that a few stimuli predominate as the input for this control in the normotensive animal. This hypothesis forms the basis for the second more important hypothesis that the functional level for control of oxygen delivery is altered through changes in the type of stimuli which predominate in the control of oxygen delivery in the hypertensive animal. Specifically, this project will investigate the relationships among oxygen and carbon dioxide content of inspired air, small artery and vein phenomena, precapillary sphincter behavior, and erythrocyte passage through capillaries for the microvasculature in skeletal muscle and skin. The relative significance of the effects of innervation, intravascular pressures, and blood gas chemistry on small artery and vein diameters and on precapillary sphincter behavior will be determined in normotensive rats and bats, and in the renovascular or spontaneously hypertensive rat. Techniques include closed-circuit television microscopy and on-line electronic analysis of video signals to allow measurements of small artery (30-120 micron m) and small vein (50-200 micron m) diameters, the duration of precapillary sphincter closure, erythrocyte flux (rbc/sec) in individual capillaries, and "capillary hematocrit".